A system for protecting against unauthorized removal of a trailer of the general type under consideration is described in Applicant's DE 10 2006 042 925 A1. The system comprises an electronic trailer braking system and also a brake assembly. An operator control device is configured to be actuated for the purpose of activating and deactivating protection against unauthorized removal of the trailer vehicle, with the result that the electronic trailer braking system is driven to effect the protection by means of the brake assembly and to apply the brakes to the trailer vehicle by means of the brake assembly in the event of unauthorized removal. The brake assembly of the trailer vehicle includes a control element that can enter at least two stable operating states. In each case, the control element remains in a stable operating state after the disconnection of the energy supply. In a first state, a spring brake is engaged. The operator control device is configured to be activated and deactivated by inputting a coded numerical value (PIN) and/or by a magnetic card and/or by a chip card and/or by means of a radio signal. This system for protection against unauthorized removal of a trailer vehicle has proved its worth but is capable of being improved with regard to operator control.